1. Technical Field
The present invention relates to a method of efficiently leaching copper from copper ore which contains chalcopyrite.
2. Related Art
One known method of recovering copper from copper ore is referred to as L-SX-EW process. According to the L-SX-EW process, copper ore is leached with sulfuric acid or the like (L=Leaching), selectively recovering copper ion from the copper-containing leachate by solvent extraction (SX=Solvent Extraction), followed by concentration, and electrolytic cathode copper is produced from the copper sulfate solution by electro-winning (EW).
In this process, among copper components contained in the copper ore, copper oxide may readily yield copper by a simple acid leaching. On the other hand, among copper components contained in the copper ore, secondary copper sulfide such as chalcocite (Cu2S) may be leached by iron (III) ion, so that copper may efficiently be leached by ferric leaching using an iron (III) ion-containing solution, or bacterial leaching making use of microorganism which can oxidize iron (II) ion in the solution into iron (III) ion.
The ferric leaching of the secondary copper sulfide ore is supposed to proceed according to the chemical reaction formula below (formula 1). Also the bacteria leaching is based on the same reaction mechanism with the ferric leaching, characterized in continuously supplying an oxidant by consecutively oxidizing iron (II) ion, produced according to (formula 1), into iron (III) ion with the aid of iron-oxidizing microorganism.Cu2S+4Fe3+→2Cu2++4Fe2++S  (formula 1)
Among copper components contained in the copper ore, primary copper sulfide such as chalcopyrite (CuFeS2) may, however, be leached remarkably slowly by the simple acid leaching, the ferric leaching and the bacterial leaching. These methods have therefore been thought to be not suitable, since it takes an extremely long time to attain a high yield of copper leaching. If it would be granted that recovery of copper from the primary copper sulfide ore is not conducted, the yield of copper leaching will stay at a low level, and the economy is diminished anyway.
On the other hand, chalcopyrite is abundant in the copper ore, so that it has been desired to recover copper also from chalcopyrite in a highly efficient manner. There have therefore been proposed various techniques for improving the leaching rate in the process of leaching from the chalcopyrite-containing copper ore. Among them, the method of leaching by adding iodine (or iodide ion) and iron (III) ion is known to improve the leaching rate from the chalcopyrite-containing copper ore, by feeding iodine as a catalyst in the form of dilute aqueous solution (Japanese Laid-Open Patent Publication Nos. 2010-024511 and 2011-042858).